---
id: "CVE-2026-98537"
kind: "vulnerability"
aliases: ["CVE-2026-98537"]
title: "Linux kernel: workqueue NULL pointer dereference during flush dependency check"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kernel", "linux", "runtime"]
not_affected_if: []
published_at: "2026-10-18T16:17:05+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98537", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel: workqueue NULL pointer dereference during flush dependency check

A kernel worker thread that is not running a work item can crash the kernel when a flush dependency check dereferences a NULL pointer. The sources describe a kernel panic path reached through an out-of-memory notifier, not code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98537

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

workqueue: Fix NULL current_pwq deref in flush dependency check

check_flush_dependency() uses current_wq_worker() to determine whether
the caller is a workqueue worker and then dereferences worker->current_pwq
to test whether the current workqueue is WQ_MEM_RECLAIM.

current_wq_worker() only means that %current has PF_WQ_WORKER set. A
kworker can reach check_flush_dependency() while it is not executing a
work item. One such path is worker_thread() acting as the pool manager,
where create_worker() does GFP_KERNEL allocation and the allocation path
invokes the OOM notifier. In that state worker->current_pwq is NULL
because current_pwq is set only by process_one_work() and cleared again
after the work function returns.

[  416.760634][  T375] Call trace:
[  416.760638][  T375]  check_flush_dependency+0x80/0x120 (P)
[  416.760648][  T375]  __flush_work+0x98/0x224
[  416.760657][  T375]  flush_work+0x30/0x44
[  416.760665][  T375]  ...
[  416.760710][  T375]  blocking_notifier_call_chain+0x58/0xa0
[  416.760719][  T375]  out_of_memory+0xb4/0x458
[  416.760730][  T375]  __alloc_pages_may_oom+0x11c/0x1a8
[  416.760739][  T375]  __alloc_pages_slowpath+0x314/0x46c
[  416.760746][  T375]  __alloc_frozen_pages_noprof+0x110/0x1a4
[  416.760753][  T375]  new_slab+0x12c/0x484
[  416.760759][  T375]  ___slab_alloc+0x7a8/0xc7c
[  416.760765][  T375]  __slab_alloc+0x74/0xd8
[  416.760772][  T375]  __kmalloc_cache_node_noprof+0x2ac/0x304
[  416.760779][  T375]  alloc_worker+0x28/0x60
[  416.760785][  T375]  create_worker+0x4c/0x20c
[  416.760790][  T375]  worker_thread+0xe8/0x2b8
[  416.760796][  T375]  kthread+0x1a8/0x200
[  416.760805][  T375]  ret_from_fork+0x10/0x20

Guard the WQ_MEM_RECLAIM-worker warning with worker->current_pwq. If the
kworker is not currently executing a work item, there is no current
workqueue to diagnose with that warning. The PF_MEMALLOC warning is left
unchanged so explicit reclaim context flushing a !WQ_MEM_RECLAIM target
is still reported.

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